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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            width: 100px;
            height: 50px;
            background-color: red;
            /* 边框
               1 solid实线
               2 dashed虚线
           */
           /*bd*/
           /* border: 1px dashed #000; */
           /* border-top:10px solid #fff;
           border-right:10px solid #fff
           border-bottom:10px solid green;
           border-left: 10px solid green; */
           /* 边框圆角 */
           border-radius: 25px;
        }
    </style>
</head>
<body>
    <div></div>
</body>
</html>